Presently available vehicle sensing systems are designed for mounting onto the bumpers of a vehicle such that only objects, animals or people in the reverse or forward paths of the vehicle may be detected. The bulk of the present market for such vehicle sensing systems is made up of acoustic (i.e. sonar-based) and Doppler-based radar devices. Due to some inherent limitations of the technologies upon which they are based, these types of devices do not work very well in obstruction filled and frequently changing spaces, such as underneath a vehicle. In fact, the area underneath a vehicle is a risk zone that is simply ignored by most manufacturers.
Acoustic devices are notorious for their poor performance regarding the elimination and filtering out of ambient noise. The vibration and noise underneath an operating vehicle obviously exacerbates this problem. Moreover, acoustic devices have less directive signal sources and receivers than common radio electronics. That is, it is extremely difficult for these devices to be focused on a specific area to the exclusion of other areas.
Doppler-based radar devices require relative motion in the radial direction between the radar transmitter and the target. Stationary targets or targets moving such that their relative radial speed is small—such as a child playing or hiding underneath parked a vehicle—may not be detected at all or until the car starts to move, which may be too late to avoid a life-threatening accident.
Furthermore, these devices (acoustic and Doppler-based radar devices) cannot discriminate between different types of materials (e.g. concrete and masonry, animal tissue, plant tissue and metals). Objects detectable using these systems are classified as present or not present. Accordingly, these devices can sometimes be overly sensitive in the areas where they do work, since not all objects represent a hazard or potential for a serious accident.